JP6104903B2 - Screen printing system and method for photovoltaic cells - Google Patents

Description

  The present invention relates to a screen printing system suitable for manufacturing a photovoltaic device, particularly suitable for printing a current collector on a photovoltaic cell. The present invention further relates to a printing method using the printing system and a method for manufacturing a photovoltaic cell incorporating the printing method. The present invention also relates to a photovoltaic cell production facility using the method. The invention also relates to a method of manufacturing the screen printing system.

  Photovoltaic cells are manufactured using a substrate made of a semiconductor material, commonly known as “wafer” in English, generally made of silicon. In particular, it is necessary to form a conductor on the surface of the substrate. Figure 1 illustrates the surface of such a substrate 1 according to current technology, which is a narrow parallel first called current collector 2 which has the role of collecting electrons generated in silicon by light. The conductor is provided. The surface of the substrate 1 is another wider, parallel conductor 3, often called a “busbar”, oriented perpendicular to the current collector 2 to carry more charge from the photovoltaic cell to the photovoltaic cell. It is further provided with a conductor serving as its role. These wider conductors 3 are generally connected to a metal strip extending over their entire length. Both of these conductors 2 and 3 are obtained by various techniques that can form a continuous conductor that extends continuously over the entire length and width of the substrate.

  In order to obtain these conductors, the current technology adopts a method of fixing the conductive ink on the substrate by screen printing once or twice, for example, by screen printing. Therefore, this method allows the conductive ink to pass through a screen made of cloth or fiber. This cloth is covered with an impermeable layer except where ink is transmitted. This permeation is performed using a squeegee that pushes the ink and permeates the cloth. However, the thread of the cloth becomes an obstacle during this operation, and particularly regarding the height uniformity of the fixed ink layer. It is impossible to obtain the ideal geometry of the conductor formed. Therefore, this method cannot form a conductor with sufficient performance. In fact, the electrical performance of this conductor is highly dependent on its geometry, especially the thickness / width ratio. However, the thickness is measured in the vertical direction perpendicular to the substrate 1, and the width is measured in the horizontal direction across the conductor.

  U.S. Pat. No. 6,258,445 describes a template secured to a frame at a portion of the periphery. This template comprises a plastic framework reinforced with metal attached. However, such an approach does not provide sufficient results.

  In order to deal with these drawbacks, the second method in the current technology is that the above-mentioned cloth is a metal template or metal sheet provided with a through-opening, and is also referred to as “stencil” using the English designation. Replace with what will be done. However, in order to prevent weakening of the metal mask and to obtain its optimum behavior during printing, it is impossible to make extremely large area openings, especially openings that extend over the entire length or width of the template. In addition, the method generally requires at least two printings using two complementary separate masks to obtain each conductor illustrated in FIG. This method is therefore complicated and costly. Furthermore, the metal mold plate does not have the flexibility of a cloth and cannot be sufficiently deformed by the action of the squeegee, so that a structure called “trampoline” provides sufficient flexibility as a whole. It is linked with the cloth adhered to the outer periphery.

  2-5 schematically show the application of this trampoline type structure to the step of screen printing a conductor on the surface of a silicon substrate 5 to form a photovoltaic cell. The printing apparatus is used to transmit a printing stand 11 on which a silicon substrate 5 is placed, and a conductive ink that forms the conductors 2 and 3 of the photovoltaic cell to be made on the surface of the silicon substrate, as already described and illustrated in FIG. And a rectangular metal plate 12 including a central printing zone 13 having openings. When forming the conductor, the metal mold 12 is positioned approximately 1 mm above the silicon substrate 5 to be printed, and the squeegee 20 extending over the entire width of the silicon substrate 5 is translated in the X direction over the entire length of the silicon substrate 5. Then, the pressure P of 30N to 150N is transmitted to the surface of the metal mold plate 12 to deform the metal model number 12, and the ink is pushed out to the surface of the silicon substrate 5 through the opening. In order to support this stress and to obtain sufficient deformation, and to allow the template to peel off after passing through the squeegee, the metal template 12 is clothed with an adhesive zone 16 extending on the four sides of the outer periphery of the rectangle. Fixed to 15. Then, the four sides forming the rectangular periphery of the cloth 15 are bonded to the rectangular frame 17.

  Nevertheless, this printing method has the following drawbacks.

-The fabric tensions the metal template, which causes deformation around the opening in the template, especially at the edges. For this reason, the width of printing is wider than desired, and an external defect is generated, which leads to a decrease in the performance of the photovoltaic cell.

-In addition, the tension of this cloth can generally cause a very delicate metal mold to be deformed to a greater extent as a whole, which leads to the bending of a line that is originally a straight line. In this case, the originally planned conductor is deformed. Furthermore, the deformation is further enhanced when the printing system is used, especially when the squeegee passes. Therefore, whether it is a second conductive ink layer to be fixed on the first layer (double printing method) or an ink layer to be fixed in an overdoped zone (selective emitter method), an ink layer in a localized zone It is very difficult to accurately stack the two, thereby impairing the performance of the photovoltaic cell.

  These drawbacks can be mitigated by using larger sized frames, for example, using a 15 inch frame instead of 12 inch for screen printing of 6 inch cells (photovoltaic cells). This is accompanied by a significant cost increase.

  Therefore, the basic object of the present invention is to propose a solution for mounting a conductor on the substrate of a photovoltaic device, which alleviates the drawbacks of the solutions according to the current technology.

  More specifically, the present invention aims to fulfill all or part of the following objectives.

  The first object of the present invention is to propose a solution for mounting a conductor in a photovoltaic cell that can optimize the performance of the photovoltaic cell formed.

  The second object of the present invention is to propose a solution for mounting a conductor on a photovoltaic cell by a highly productive, excellent performance and economical method.

  Therefore, the present invention is a screen printing system including a metal mold plate, and the cloth fixed to the metal mold plate has at least one free end, thereby reducing or eliminating the deformation caused by the action of the squeegee. It is related with the system characterized. The fabric can have a free part at its outer periphery.

  The present invention also relates to a manufacturing facility for a photovoltaic device comprising the screen printing system as described above.

  The present invention also provides a screen printing method by the screen printing system as described above, which includes a step of squeegee operation of a template that causes movement of a free end of a cloth fixed to the metal template. Also related to the method.

  The method for manufacturing a photovoltaic cell device may include a step of screen printing a conductor on a silicon substrate using a screen printing system as described above.

  The invention is defined in more detail in the claims.

  The objects, features and advantages of the present invention are explained in detail in the following description of specific embodiments prepared as non-limiting in connection with the accompanying drawings.

It is the schematic which showed the conductor of the surface of the photovoltaic cell by the present technique. 1 is a schematic cross-sectional view of a screen printing system having a trampoline structure for printing a conductor on the surface of a photovoltaic cell according to the current technology. 1 is a schematic top view of a screen printing system having a trampoline structure according to the current technology. 1 is a schematic cross-sectional view perpendicular to the X axis of a screen printing system having a trampoline structure according to current technology. 1 is a schematic cross-sectional view parallel to the X axis of a screen printing system having a trampoline structure according to current technology. 1 is a top view of a portion of a screen printing system according to an embodiment of the present invention. FIG. 6 is a top view of a portion of a screen printing system according to a variation of an embodiment of the present invention. FIG. 6 is a top view of a portion of a screen printing system according to a variation of an embodiment of the present invention. FIG. 6 is a top view of a portion of a screen printing system according to a variation of an embodiment of the present invention.

  In the following description, for the sake of simplicity, similar elements are designated using the same reference numerals in different drawings, even if they have different shapes and / or properties.

  FIG. 6 shows an embodiment of the present invention. This screen printing system also uses a trampoline structure. Thus, the system comprises a rectangular metal template 12, which is secured to the fabric 15 by gluing or any other fastening device over its peripheral zone 16 extending along the four sides of the rectangular outer periphery. The However, the cloth 15 is not fixed to the frame over the entire outer periphery. In fact, only the two sides 151 and 152 of this cloth, which are arranged perpendicular to the movement direction X of the squeegee, are fixed to the two sides 171 and 172 of the support frame 17 by some fixing device 18 such as bonding, respectively. Is done. On the other hand, the lateral sides 153 and 154 of the cloth have free ends that are not fixed to the frame. In this embodiment, there is no advantage that the metal plate 12 is not stretched in the lateral direction due to the action of the pressure of the squeegee, and printing defects caused by the phenomenon are eliminated.

  In other words, in this solution, the fabric 15 is fixed over the entire outer periphery of the metal template to form a trampoline type assembly as described above. This assembly is free of part of its outer periphery, thereby reducing or eliminating deformation of the metal template during the production of the printing system and during its operation due to the action of the squeegee. The cloth 15 has the effect of stretching a metal mold on the support frame. In the case of adopting this geometric shape, the effect of reducing or eliminating the deformation of the metal plate is particularly obtained in the moving direction of the squeegee.

  The outer fabric 15 is advantageously made of a yarn fabric, and the yarn may be a metal, but is preferably organic (polyester, polyamide, polyarylate) for cost reduction, preferably for more flexibility. Is made of polyester.

  FIGS. 7-9 show several alternative embodiments, in which the fabric 15 is between the fabric 15 and the frame 17, more precisely, the opposite sides 153, 154 of the fabric and the frame 17. Are fixed to the frame 17 over their outer peripheries except for the two zones at the level of the lateral sides 153 and 154 on both sides of the fabric that define openings 183 and 184 respectively between the sides 173 and 174. In a variant, these openings 183, 184 are obtained simply by the free end of the cloth 15 in the frameless part.

  In these alternative embodiments, the openings 183, 184 are substantially parallel to the outer arms 173, 174 of the frame 17 and are substantially on the extension of the printed pattern defined by the through-openings in the metal template 12, It has a linear shape centered with respect to the through opening. The opening extends not over the entire length of the fabric but over a length L that is substantially the same as the length M of the printed pattern defined by the metal template 12. However, the length M is measured in a direction substantially parallel to the arms 173 and 174 of the frame 17 and / or the sides 153 and 154 of the cloth. In a variant, the openings have different lengths L, preferably in the range from M-30 mm to M + 80 mm (L and M are in mm). Advantageously, the openings are slightly above the dimension M of the printed pattern and ideally have a length L of around M + 25 mm (i.e. for example a length of 156 mm, i.e. a 6 inch substrate (wafer)). (In the example of a typical length implementation of the pattern printed on top, for printing 153mm metallization, the fabric lateral sides 153, 154 with free ends not fixed to the frame are 170mm long) . This length L, which is preferably less than the length of the fabric, i.e. less than the total length of the sides 153, 154 of the fabric 15, gives the fabric 15 a slight lateral tension at the end level against the metal template. Is possible.

  In fact, it is advantageous to maintain a minimum lateral tension so that the metal template remains stretched in two directions. Therefore, it is desirable that part of the lateral tension transmitted by the cloth remains at the end. However, the template portion corresponding to the printing zone must not be subjected to lateral tension so that the printing zone will not be deformed. Therefore, as described above, the side portions 153 and 154 of the cloth having free ends that are not fixed to the frame at the opening level or the like are provided at the level of the printing zone of the template, and the through opening of the template defining the printing pattern is provided. The dimensions are determined according to the size.

  The openings 183 and 184 can be obtained by various methods such as not bonding the cloth to the frame or cutting the cloth after bonding the cloth as in the related art. Furthermore, according to another variant embodiment, such an opening may have a curved shape rather than a straight line, unlike the previous example.

  FIGS. 8 and 9 show that the frame 17 has a portion 175 at the level of the opening that serves to reduce the risk of filing the end of the fabric 15 at the level of the openings 183, 184 between the fabric. The modification which it has is shown. This portion 175 can be obtained by applying any kind of adhesive to the free end of the fabric 15. In fact, it is desirable that the cloth breaks from a zone that is not fixed to the frame, such as a non-adhesive part, i.e., that the yarn does not loosen at the free end level from the lateral sides 153, 154 of the cloth. . The free zone of this fabric can advantageously be stabilized using the same adhesive material used for the frame / fabric bond (or the metal template and the fabric), in which case As indicated by 8 portion 175, the adhesive adhesion is offset inward so that it does not touch the frame in the zone where it is desired to remain free. In the variant shown in FIG. 9, the fabric 15 could first be glued to the frame 17 on four sides, and then a zone could be cut out again within the frame. At that time, a line of additional adhesive is added to the cloth so as to surround the portion of the cloth to be cut, so that the cracks do not occur at the level of the openings 183 and 184 finally obtained.

  In a variant not shown, the square metal template provided in the screen printing system is fixed to the cloth in a narrow zone and does not extend further on the four sides of the cloth's rectangular periphery. Actually, only the two sides of the template arranged in the direction perpendicular to the moving direction X of the squeegee are fixed to the two sides of the outer cloth by a fixing device such as bonding. On the other hand, the side portion of the metal mold plate is not fixed to the cloth or the frame, and remains free. The cloth is fixed to the four sides with respect to the frame over the entire outer periphery thereof.

  The invention has been described by way of specific embodiments by way of example. The present invention more generally relates to a screen printing system comprising a metal mold, wherein the fabric secured to the metal mold comprises at least one free end to reduce or reduce its deformation due to the action of the squeegee. Applies to any system characterized by elimination. As such, templates and fabrics have shapes and dimensions different from those described above, and have different free ends than described, e.g. over less or greater lengths and / or different numbers of free ends. It can have.

  Finally, the present invention further comprises a screen printing characterized in that it includes a fixing method for fixing the fabric to the metal template so as to leave at least one free end, thereby reducing or eliminating its deformation due to the action of the squeegee. It also relates to the system manufacturing method.

  The present invention is also a step of performing printing through a template to attach a conductive ink layer to the surface of the substrate. The ink is pushed into the opening at the center of the template and the cloth fixed to the metal template is used. It also relates to a method for producing a conductor on a substrate using a printing system as described above, characterized in that it comprises the step of allowing a plurality of conductors to be formed by a squeegee that causes movement of the free end.

  This printing method is a method for manufacturing a photovoltaic device, and is particularly interesting as a manufacturing method for forming all or part of a surface conductor such as a current collecting conductor and / or a bus bar type conductor.

  In particular, this printing electrically couples a discontinuous first conductor, which is interrupted at least at the level of the interconnect zone, with the interconnect zone of the first conductor being covered by at least one second conductor. Can be formed along the first direction. This electrical coupling step is advantageously accomplished by fixing the metal strip by welding or gluing.

  The present invention also relates to a photovoltaic device manufacturing facility comprising the above-described screen printing system for performing the conductor printing method.

Claims (15)

  A screen printing system comprising a metal mold plate (12) and a cloth (15) fixed over the entire outer periphery of the metal mold plate (12) to form a trampoline-like assembly, wherein the metal mold plate (12 A screen printing system characterized in that deformation due to the action of the squeegee (20) is reduced or eliminated by the cloth (15) fixed to the squeegee having at least one free end.   The cloth (15) has a free part at its outer periphery, by being not fixed to the support frame (17) and / or through at least one opening (183, 184) provided at the level of its periphery The screen printing system according to claim 1, wherein   The screen printing system according to claim 1 or 2, characterized in that the fabric (15) comprises metal yarns and / or yarn fabrics such as organic yarns of the class polyester, polyamide, polyacrylate.   The metal template (12) is rectangular, and the free end of the cloth (15) fixed to the metal template (12) is parallel to the moving direction of the squeegee (20) of the printing system. 4. Screen printing system according to any one of claims 1 to 3, characterized in that it comprises all or part of the ends of the two lateral sides (153, 154) of the fabric in the direction.   The other two sides (151, 152) of the cloth (15) fixed to the metal template (12) in a direction perpendicular to the moving direction of the squeegee (20) of the printing system, 5. The screen printing system according to claim 4, wherein the screen printing system is fixed to the support frame (17).   The cloth (15) has at least one free end provided on one side (153, 154) of the cloth (15), and the free end so that tension acting in two directions is maintained. 6. The screen printing system according to claim 1, wherein a length L of the screen is less than a length of the side of the cloth.   The metal template (12) is provided with a through opening that defines a printed pattern of length M (unit: mm) as measured in the direction of the free end of the cloth (15), the free end of which is from M-30 mm The screen printing system according to claim 1, wherein the screen printing system has a length L (unit: mm) in a range of M + 80 mm.   The metal template (12) is provided with a through opening that defines a printed pattern of length M as measured in the direction of the free end of the fabric (15), the free end exceeding the length M of the pattern. The screen printing system according to any one of claims 1 to 6, wherein the screen printing system has a length L.   9. The free end of the fabric (15), characterized in that it is substantially centered with respect to the printed pattern defined by the through opening of the metal template (12). Screen printing system.   10.The level of at least a portion of the free end of the fabric (15), including the attachment of a class of adhesives to prevent rupture from occurring. Screen printing system.   The screen printing system according to any one of claims 1 to 10, wherein the screen printing system is a part of a facility for printing conductors on a photovoltaic device.   A facility for manufacturing a photovoltaic device, comprising the screen printing system according to any one of claims 1 to 10.   A screen printing method using the screen printing system according to any one of claims 1 to 10, wherein the mold causes movement of a free end of a cloth (15) fixed to the metal mold plate (12). A printing method comprising a step of squeegeeing a board.   A method for manufacturing a photovoltaic device, comprising the step of screen-printing a conductor on a silicon substrate using the screen printing system according to claim 1.   It includes the step of fixing the cloth (15) fixed to the metal template (12) having at least one free end, thereby reducing or eliminating the deformation caused by the action of the squeegee (20). A method for manufacturing a screen printing system according to any one of claims 1 to 10.

Images